A power transmitting apparatus is largely divided into a rack and pinion for converting a rotational motion to a linear motion or vice versa and a gear train for transmitting only a rotational motion while converting a rotational speed and a torque.
Typically, a power transmitting system of a power transmitting apparatus mainly uses a tooth shape according to an involute curve principle. However, there is a rare case of using a tooth shape according to a cycloid curve principle and a pin gear.
No matter what tooth is used, lubrication of a contact tooth surface is essential in the power transmitting apparatus. In particular, when a pre-pressure is applied to a tooth surface in order to improve a degree of precision or rigidity, a large amount of friction is generated on the tooth surface so that importance of lubrication is further emphasized.
The lubrication may be essential not only for a rack and pinion for converting a rotational motion to a linear motion or a linear motion to a rotational motion, but also for a portion where a driving gear and a driven gear are engaged with each other, such as, a section gear, a large index, or a large positioner needing a circular motion of a large diameter.
In a related art, for supply of a lubricant, a lubrication method of entirely surrounding a gear train by a housing and performing an oil leak prevention treatment using an oil seal or an O-ring and then filling the inside of the housing with the lubricant, or an oil bath lubrication method, has been selected.
However, it is a problem that this method is difficult to apply because an increase of self-weight and deterioration of efficiency due to viscosity friction of a lubricant, particularly in a case of a large gear train.
In the meantime, for a rack and pinion and a section gear, since these are not a gear train performing a complete circular motion and the gear train is exposed to the outside, there has been no special method other than a method of regularly coating a lubricant having a high viscosity. When the lubricant is regularly coated, maintenance and repair is needed due to the adherence of external dust and efflorescence of a lubricant. Furthermore, a lubrication work becomes inconvenient and difficult. Therefore, a solution to address the above matters is needed.